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Hamza Bin Laden, who was groomed by his fanatical father from an early age, also called on Islamists in Saudi Arabia to rise up and overthrow the US-backed government.

He said all al-Qaeda sympathisers should pledge allegiance to the group's offshoot in the Arabian Peninsula (AQAP), described as the deadliest wing of the extremist network.

According to the SITE Intelligence Group which monitors terror chatter online, the 23-year-old is seeking to unify the jihadi movement around the deaths of Muslims in conflicts in Syria and Palestine as well as over Western support for Saudi Arabia.

In a 21-minute speech entitled "We Are All Osama" which was recorded in July, he said: "We will continue striking you and targeting you in your country and abroad in response to your oppression of the people of Palestine, Afghanistan, Syria, Iraq, Yemen, Somalia and the rest of the Muslim lands that did not survive your oppression."

Death of Osama Bin Laden: In Pictures

In pictures: Death of Osama Bin Laden

Hamza was at his father's side in Afghanistan before the 9/11 attacks and spent time with him in Pakistan.

Said to be the favourite son of Osama, he was groomed from an early age as a potential successor.

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Saudi Arabia and the US have maintained close ties

GETTY

Osama Bin Laden was the world's most wanted man

His call to arms follows a chilling message from the leader of Al-Qaeda urging the terror group's fanatics to kidnap westerners.

Ayman al-Zawahiri called on jihadis to take hostages who are "enemies of Islam" and exchange them for jailed militants.

The Al-Qaeda leader called for the liberation of every terrorist until "the last Muslim male prisoner and last Muslim female prisoner in the prisons of the Crusaders, apostates, and enemies of Islam" has been released.